The present invention relates to a profile and feeding state detection apparatus and method for a paper sheet to be fed into an inspection apparatus for determining the condition and authenticity (i.e., counterfeit nature) of a paper sheet such as a banknote and, more particularly, to a detection apparatus and method for detecting the width, damage, skew, misalignment, puncture, or dog ear of the paper sheet.
A conventional profile and feeding state detection apparatus of the type described above has a configuration as shown in FIG. 1. A light source 1 directs light onto the lower surface of a paper sheet P which is fed in the feeding direction indicated by arrow a. Rod-shaped photocells 3 and 5 are disposed above the paper sheet P and oppose the light source 1 through the paper sheet P. The beams of light from the light source 1 which are transmitted through the paper sheet P are incident on the photocells 3 and 5. Output signals from the photocells 3 and 5 are amplified by amplifiers 7 and 9 respectively. The amplified signals are then supplied to a processing circuit 11. The photocells 3 and 5 are disposed at the two edges (width-wise) of the paper sheet P in the direction perpendicular to the feeding direction indicated by arrow a. When the paper sheet P is fed below the photocells 3 and 5, the light beams to be incident on the photocells 3 and 5 are shielded in accordance with the width (direction perpendicular to the feeding direction indicated by arrow a), damage, punctures, dog ears, etc. of the paper sheet P. At this time, the output signals from the photocells 3 and 5 are supplied to and amplified by the amplifiers 7 and 9 respectively. The amplified signals are then supplied to the processing circuit 11. In the processing circuit 11, each amplified signal is integrated for a predetermined time interval. Integrated values are used to detect the width and any damage, misalignment, or puncture of the paper sheet P.
In the conventional detection apparatus for detecting the width, damage, misalignment and puncture of the paper sheet P, when a dog ear is present in the paper sheet P or when the paper sheet P is damaged, output signals from the photocells 3 and 5 are greatly changed. As a result, a large error occurs in the integrated value of the output signal. For example, the integrated value may appear to indicate that the width of the paper sheet P is decreased. The detection apparatus then erroneously less than it should be that the paper sheet P has a width smaller than its actual width. In this condition, proper width and misalignment detection cannot be performed.
Similarly, the above integrated value may appear to indicate that the paper sheet P is damaged. Furthermore, the value may appear to indicate that a puncture (hole) is present in the paper sheet P. In this manner, even if the paper sheet P is neither damaged nor punctured, the detection apparatus erroneously detects that a damaged portion or a puncture is present which can result in greater inconvenience. Furthermore, proper detection cannot be performed when the paper sheet P such as a banknote is very thin, or when an old and worn banknote is used. For example, when a new banknote is used, the amount of light transmitted through the banknote is greater than that transmitted through an old, worn banknote. Therefore, the integrated value obtained by detecting the new banknote appears to indicate that its width is decreased in the same manner as in instances where the detection apparatus erroneously detects that the paper sheet has a damaged portion or a puncture. As a result, the detection apparatus erroneously detects that the new banknote has a width shorter than the standard width (or the detection apparatus erroneously detects that the new banknote has a damaged portion or a puncture). However, when an old banknote is used, the amount of light transmitted therethrough is smaller than that transmitted through a new banknote. The integrated value obtained by detecting the old banknote appears to indicate that its width is greater than it actually is (or the detecting apparatus erroneously detects that the old banknote does not have any damaged portion or puncture). The old banknote can be detected to have a width greater than the standard width, or to have no damaged portion or puncture, even if the old banknote has many damaged portions or punctures.
Another conventional skew detection apparatus is shown in FIG. 2. A pair of photosensors 13 and 15 are disposed in the direction perpendicular to the feeding direction indicated by arrow a and are spaced apart from one another. Skew detection is performed such that a time interval T.sub.sk (sec) from the moment when one corner of the leading edge of the paper sheet P passes the first one of the photosensors 13 and 15 to the moment when the other corner of the leading edge of the paper sheet P passes the second one of the photosensors 13 and 15 is measured using a unit time interval T.sub.cp (sec/m). Using the measured time interval T.sub.sk (sec), a distance L.sub.A (m) of the skewed paper sheet P is calculated from equation (I). Furthermore, using the obtained distance L.sub.A (m) and a distance L.sub.B (m) between the photosensors 13 and 15, a skew angle .theta. is calculated from equation (II) below: EQU L.sub.A =T.sub.sk /T.sub.cp (I) EQU .theta.=tan.sup.-1 (L.sub.A /L.sub.B) (II)
However, in the conventional skew detection apparatus described above, when the paper sheet P has a dog ear (B in FIG. 3) or a damaged corner, a large error occurs in the measured value. Therefore, highly precise and accurate skew measurement cannot be performed.
FIG. 4 shows a conventional dog ear detection apparatus. Light sources 17 and 19 radiate light beams from above the paper sheet P fed in the feeding direction indicated by arrow a. Photocells 21 and 23 respectively oppose the light sources 17 and 19 and sandwich the paper sheet P. The photocells 21 and 23 receive light beams from the light sources 17 and 19, respectively. Output signals from the photocells 21 and 23 are amplified by amplifiers 25 and 27, respectively. The amplified signals are then supplied to a processing circuit 29. The photocells 21 and 23 are disposed at the two side edges (i.e., the edges defining the width) of the paper sheet P in the direction perpendicular to the feeding direction indicated by arrow a. When the paper sheet P is fed under the light sources 17 and 19, the light beams from the light sources 17 and 19 are shielded in accordance with the size of the dog ear of the paper sheet P. At this time, the output signals from the photocells 21 and 23 are amplified by the amplifiers 25 and 27, respectively, and are then supplied to the processing circuit 29. The processing circuit 29 counts each output signal for a predetermined time interval to detect a folded size l.
However, in the dog ear detection apparatus of the type described above, when the paper sheet P is misaligned or when the sizes of the paper sheets differ slightly, the output signals from the photocells 21 and 23 will vary greatly, resulting in a large error in the count value. As shown in FIGS. 5A to 5D, misalignment and variation in the size of the paper sheet results in a change in the folded size l. Therefore, the detected folded size is determined to be smaller than the actual folded size.